Effect of water and protic solvents on polysaccharide-based column efficiency

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Polysaccharide-based columns are widely used in chiral chromatography.
• Mobile phase composition significantly affects chromatographic performance, including enantiomer resolution and mass transfer.
• Acetonitrile is a common organic modifier in reversed-phase HPLC mobile phases.

Purpose of the Study:

• To evaluate the impact of replacing acetonitrile with water and protic solvents (methanol, ethanol) in the mobile phase on polysaccharide-based chiral column efficiency.
• To investigate the effects of varying water content in combination with protic solvents on mass transfer and column plate height.
• To determine optimal mobile phase conditions for chiral separations, particularly at higher flow rates.

Main Methods:

• Utilized polysaccharide-based columns for chromatographic analysis.
• Systematically varied mobile phase composition, replacing acetonitrile with water, methanol, and ethanol.
• Analyzed column efficiency by measuring column plate height and examining van Deemter plots.
• Evaluated performance at different flow rates, focusing on conditions above 1 mL/min for a 4.6 mm column.

Main Results:

• Increased water content generally improved enantiomer resolution but adversely affected mass transfer.
• The combination of water with methanol and ethanol negatively impacted column plate height.
• Ethanol exhibited more pronounced adverse effects on mass transfer compared to methanol.
• Van Deemter plots often lacked an optimal minimum point within the tested flow rate range.
• Acetonitrile-based mobile phases demonstrated superior performance in mitigating these adverse effects.

Conclusions:

• Water and protic solvents (methanol, ethanol) can negatively influence mass transfer and column efficiency in polysaccharide-based chiral chromatography.
• Acetonitrile and its aqueous mixtures are recommended mobile phases to maintain optimal column performance, especially at flow rates exceeding 1 mL/min.
• Careful consideration of mobile phase composition is crucial for achieving efficient chiral separations and avoiding suboptimal chromatographic conditions.